653 research outputs found
Network Coding Tree Algorithm for Multiple Access System
Network coding is famous for significantly improving the throughput of
networks. The successful decoding of the network coded data relies on some side
information of the original data. In that framework, independent data flows are
usually first decoded and then network coded by relay nodes. If appropriate
signal design is adopted, physical layer network coding is a natural way in
wireless networks. In this work, a network coding tree algorithm which enhances
the efficiency of the multiple access system (MAS) is presented. For MAS,
existing works tried to avoid the collisions while collisions happen frequently
under heavy load. By introducing network coding to MAS, our proposed algorithm
achieves a better performance of throughput and delay. When multiple users
transmit signal in a time slot, the mexed signals are saved and used to jointly
decode the collided frames after some component frames of the network coded
frame are received. Splitting tree structure is extended to the new algorithm
for collision solving. The throughput of the system and average delay of frames
are presented in a recursive way. Besides, extensive simulations show that
network coding tree algorithm enhances the system throughput and decreases the
average frame delay compared with other algorithms. Hence, it improves the
system performance
Multi-slot Coded ALOHA with Irregular Degree Distribution
This paper proposes an improvement of the random multiple access scheme for
satellite communication named Multislot coded ALOHA (MuSCA). MuSCA is a
generalization of Contention Resolution Diversity Slotted ALOHA (CRDSA). In
this scheme, each user transmits several parts of a single codeword of an error
correcting code instead of sending replicas. At the receiver level, the decoder
collects all these parts and includes them in the decoding process even if they
are interfered. In this paper, we show that a high throughput can be obtained
by selecting variable code rates and user degrees according to a probability
distribution. With an optimal irregular degree distribution, our system
achieves a normalized throughput up to 1.43, resulting in a significant gain
compared to CRDSA and MuSCA. The spectral efficiency and the implementation
issues of the scheme are also analyzed.Comment: 6 pages, 8 figure
Sign-Compute-Resolve for Random Access
We present an approach to random access that is based on three elements:
physical-layer network coding, signature codes and tree splitting. Upon
occurrence of a collision, physical-layer network coding enables the receiver
to decode the sum of the information that was transmitted by the individual
users. For each user this information consists of the data that the user wants
to communicate as well as the user's signature. As long as no more than
users collide, their identities can be recovered from the sum of their
signatures. A splitting protocol is used to deal with the case that more than
users collide. We measure the performance of the proposed method in terms
of user resolution rate as well as overall throughput of the system. The
results show that our approach significantly increases the performance of the
system even compared to coded random access, where collisions are not wasted,
but are reused in successive interference cancellation.Comment: Accepted for presentation at 52nd Annual Allerton Conference on
Communication, Control, and Computin
From 5G to 6G: Has the Time for Modern Random Access Come?
This short paper proposes the use of modern random access for IoT
applications in 6G. A short overview of recent advances in uncoordinated medium
access is provided, highlighting the gains that can be achieved by leveraging
smart protocol design intertwined with advanced signal processing techniques at
the receiver. The authors' vision on the benefits such schemes can yield for
beyond-5G systems is presented, with the aim to trigger further discussion.Comment: 2 pages, 1 figure, presented at 6G Summit, Levi, Finland, 201
Broadcast Coded Slotted ALOHA: A Finite Frame Length Analysis
We propose an uncoordinated medium access control (MAC) protocol, called
all-to-all broadcast coded slotted ALOHA (B-CSA) for reliable all-to-all
broadcast with strict latency constraints. In B-CSA, each user acts as both
transmitter and receiver in a half-duplex mode. The half-duplex mode gives rise
to a double unequal error protection (DUEP) phenomenon: the more a user repeats
its packet, the higher the probability that this packet is decoded by other
users, but the lower the probability for this user to decode packets from
others. We analyze the performance of B-CSA over the packet erasure channel for
a finite frame length. In particular, we provide a general analysis of stopping
sets for B-CSA and derive an analytical approximation of the performance in the
error floor (EF) region, which captures the DUEP feature of B-CSA. Simulation
results reveal that the proposed approximation predicts very well the
performance of B-CSA in the EF region. Finally, we consider the application of
B-CSA to vehicular communications and compare its performance with that of
carrier sense multiple access (CSMA), the current MAC protocol in vehicular
networks. The results show that B-CSA is able to support a much larger number
of users than CSMA with the same reliability.Comment: arXiv admin note: text overlap with arXiv:1501.0338
Characterization of Coded Random Access with Compressive Sensing based Multi-User Detection
The emergence of Machine-to-Machine (M2M) communication requires new Medium
Access Control (MAC) schemes and physical (PHY) layer concepts to support a
massive number of access requests. The concept of coded random access,
introduced recently, greatly outperforms other random access methods and is
inherently capable to take advantage of the capture effect from the PHY layer.
Furthermore, at the PHY layer, compressive sensing based multi-user detection
(CS-MUD) is a novel technique that exploits sparsity in multi-user detection to
achieve a joint activity and data detection. In this paper, we combine coded
random access with CS-MUD on the PHY layer and show very promising results for
the resulting protocol.Comment: Submitted to Globecom 201
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